Project Summary Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne human pathogen in China, Japan and South Korea. The vector, Haemaphysalis longicornis, was recently discovered in the United States, and as such, could play a role in viral emergence in North America. Surveillance efforts in endemic regions show seroconversion and occasional viral RNA in domestic animals and select wildlife, thus indicating the likelihood for zoonotic transmission of the virus. Presently, our knowledge about host competence and clinical disease in animals is limited, and this study seeks to elucidate the mechanism for viral amplification and pathogenesis in vertebrate hosts. This information will be key to understanding the ecology of SFTSV and will provide guidance for surveillance and monitoring efforts. We will inoculate North American wildlife species with ecological relevance to Asian species to look for competent reservoir hosts should SFTSV emerge in the United States. Additionally, we will develop a relevant vector-host model for performing vector competence studies with H. longicornis using domestic goats, which are a likely source of the virus. These experiments are expected to provide strong evidence regarding species of interest in disease transmission and spread and provide vital information about the tick vector.